Thermally conductive molding compound structure for heat dissipation in semiconductor packages

ABSTRACT

The present disclosure, in some embodiments, relates to a method of forming a semiconductor package. The method may be performed by attaching a first thermal conductivity layer to an upper surface of a first chip, and attaching a second thermal conductivity layer to an upper surface of a second chip. A first support substrate is attached to lower surfaces of the first chip and the second chip. A molding compound is formed over the first support substrate and laterally surrounds the first chip and the second chip. The first support substrate is replaced with a package substrate after forming the molding compound over the first support substrate.

REFERENCE TO RELATED APPLICATIONS

This Application is a Divisional of U.S. application Ser. No. 15/966,426, filed on Apr. 30, 2018, which is a Continuation-in-Part of U.S. application Ser. No. 14/076,487, filed on Nov. 11, 2013 (now U.S. Pat. No. 9,960,099, issued on May 1, 2018). The contents of the above-referenced Patent Applications are hereby incorporated by reference in their entirety.

BACKGROUND

Poor heat dissipation is a common issue for microelectronics device packages. Semiconductor chips, especially those with high thermal design power (TDP) requirements can result in localized overheating that can be deleterious to product yield, performance and reliability of the resulting microelectronics device packages. A thermal management device, such as a heat sink, is typically placed on the backside of wafers for heat to be transported through a molding compound encapsulating a surface of the wafer to the surrounding environment. However, the molding compound, which is typically a mixture of an epoxy and a silica filler, has a low thermal conductivity that is generally in the range of 0.6 W/m-K to 0.8 W/m-K. This can make the molding compound a barrier to heat dissipation.

For some processes where the thermal management device is attached to the wafer, a back-side grinding process is needed to reduce the thickness of the molding compound. However, such grinding process may cause the molding compound to become undone or delaminated from the wafer to which it is attached. Where this has occurred, the edges of chips of the wafer may be susceptible to cracking, chipping and/or exposed to corrosive environmental influences during a subsequent die cutting process and associated handling.

BRIEF DESCRIPTION OF DRAWINGS

Embodiments of the present disclosure are best understood from the following detailed description when read with the accompanying figures. It is emphasized that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.

FIG. 1 is a flowchart of a method of fabricating a semiconductor package, according to one or more embodiments of the present disclosure.

FIG. 2 is a cross-sectional view of semiconductor packages after wafer singulation, according to one or more embodiments of the present disclosure.

FIG. 3 is a cross-sectional view of semiconductor packages after wafer singulation, according to one or more embodiments of the present disclosure. FIG. 4 is a cross-sectional view are semiconductor packages having different shapes of thermal conductivity layers, according to one or more embodiments of the present disclosure.

FIGS. 5-8 are cross-sectional views of a portion of a semiconductor package at various stages of fabrication according to one or more embodiments of the present disclosure.

FIGS. 9-11 are cross-sectional views of a portion of a semiconductor package at various stages of fabrication according to one or more embodiments of the present disclosure.

FIGS. 12-16 are cross-sectional views of a portion of a semiconductor package at various stages of fabrication according to one or more alternative embodiments of the present disclosure.

DETAILED DESCRIPTION

In the following description, specific details are set forth to provide a thorough understanding of embodiments of the present disclosure. However, one having ordinary skill in the art will recognize that embodiments of the disclosure can be practiced without these specific details. In some instances, well-known structures and processes are not described in detail to avoid unnecessarily obscuring embodiments of the present disclosure.

Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present disclosure. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. It should be appreciated that the following figures are not drawn to scale; rather, these figures are intended for illustration.

FIG. 1 is a flowchart of a method 2 of fabricating a semiconductor package according to various aspects of the present disclosure. Referring to FIG. 1, the method 2 includes block 4, in which a chip is provided having a first surface and a second surface. The method 2 includes block 6, in which a thermal conductivity layer is formed attached to the first surface of the chip. The thermal conductivity layer provides a path through which heat generated from the chip is dissipated to the surrounding environment to prevent chip overheating. The method 2 includes block 8, in which a substrate is provided. The substrate is attached to the second surface of the chip. The method 2 includes block 10, in which a molding compound is formed above the substrate to encapsulate the chip and the thermal conductivity layer.

In some embodiments, additional processes are performed before, during, or after the blocks 4-10 shown in FIG. 1 to complete the fabrication of the semiconductor package, but these additional processes are not discussed herein in detail for the sake of simplicity.

FIGS. 2-10 are cross-sectional side views of portions of a semiconductor package at various stages of fabrication according to one or more embodiments of the method 2 of FIG. 1. FIGS. 2-10 have been simplified for a better understanding of the inventive concepts of the present disclosure. It should be appreciated that the materials, geometries, dimensions, structures, and process parameters described herein are exemplary only, and are not intended to be, and should not be construed to be, limiting. Many alternatives and modifications will be apparent to those skilled in the art, once informed by the present disclosure.

Referring to FIG. 2, a first chip 100 is provided. First chip 100 is a heat sensitive chip such as a memory chip, logic chip, processor chip, or the like. A thermal conductivity layer 120 is attached to a surface of first chip 100 by an optional adhesive layer 110. In some embodiments, the adhesive layer 110 comprises one or more of an adhesive bonding, tape bonding, resin bonding, or other suitable material.

The thermal conductivity layer 120 is attached on top of first chip 100 to provide a high degree of heat dissipation by providing a thermal path through which thermal energy, or heat that is generated by first chip 100, is dissipated to the surrounding environment. The higher thermal conductivity enables the thermal conductivity layer 120 to function as an integrated heat spreader to dissipate heat from first chip 100. In addition to thermal management, the thermal conductivity layer 120, in some embodiments, is also configured to provide mechanical support during a molding process to minimize shrinkage and/or warping of a molding compound supplied during the molding process. In one or more embodiments, thermal conductivity layer 120 is capable of being used in an integrated circuit packaging type or technology, including, but not limited to, wire bonded packages, flip chip molded matrix array packages (FCMMAP), and other packages that couple an integrated circuit die to second level interconnects such as a ball grid array, a land grid array, and/or a pin grid array.

In accordance with various embodiments of the present disclosure, the thermal conductivity layer 120 has a thermal conductivity that is high enough to provide sufficient passive cooling for the integrated circuit package. For instance, in some embodiments of the present disclosure, the thermal conductivity layer 120 has a thermal conductivity between about 3 W/m-K and about 10 W/m-K. In some embodiments, depending on the specific materials used in the thermal conductivity layer 120, the thermal conductivity of the thermal conductivity layer 120 is higher than 10 W/m-K.

In one or more embodiments, the thermal conductivity layer 120 comprises a metal, such as copper, copper alloy, aluminum, gold or other suitable metals deposited on first chip 100. In some embodiments, the thermal conductivity layer 120 is deposited on the first chip 100 by an electrochemical plating (ECP) process and/or a sputtering technique. In an ECP process, the thermal conductivity layer 120 is, for example, blanket deposited on the first chip 100. In some embodiments, depending on chip size, chip spacing and the technology employed, the thickness of the thermal conductivity layer 120 ranges from about 0.5 microns to about 300 microns. An exemplary ECP process involves an electroplating composition having current density of about 3 A/cm² to about 60 A/cm². In some embodiments, the plating bath includes any combination of CuSO₄, HCl, H₂SO₄, suppressor(s) and additives. In some embodiments, the ECP solution is maintained at a temperature of about 20 ° C. to about 40° C. and a pH in the range of about 1-7. The current density of the ECP solution is about 3 A/cm² to about 60 A/cm². According to various embodiments, the ECP process is continued for a specified duration of time or until the first chip 100 is covered with the thermal conductivity layer 120. In some embodiments, the duration and the intensity of the ECP process are adjustable on demand.

In various embodiments, a sputtering process, such as a copper sputtering process, is used to deposit the thermal conductivity layer 120 on first chip 100. Sputtering is also known as physical vapor deposition (PVD). Although a PVD method is capable of forming a copper or copper alloy layer without introducing impurities, PVD typically has a lower deposition rate than an ECP process.

In one or more embodiments, the thermal conductivity layer 120 is deposited by chemical vapor deposition (CVD), plasma-enhanced CVD (PECVD), atomic layer deposition (ALD), evaporation, and/or other suitable processes.

In some embodiments, the thermal conductivity layer 120 is a thermally conductive adhesive layer that includes a conductive filler material comprising one of more of silver (Ag), copper (Cu), gold (Au), aluminum (Al), solder, carbon related materials such as carbon nanotubes, carbon fibers, graphite, combinations of these or other conductive materials. The use of a thermally conductive filler material substantially increases the overall thermal conductivity of the adhesive layer. Carbon nanotubes, for example, used in connection with an adhesive tape type material are capable of being arranged in the tape using a variety of approaches.

In some embodiments, carbon nanotubes are grown in a generally vertical direction from a material used in the tape. Catalyst material is arranged where growth is desirable, and a carbon-containing gas is introduced to the catalyst material. Carbon nanotubes are grown extending generally away from the catalyst material. After growth, the area around the carbon nanotubes is filled with base material including, for example, one or more adhesives, compliant plastics, and insulative material. Surfaces of the tape are arranged with an adhesive, using for example, an adhesive base material and/or adding an adhesive material at the surface.

In some embodiments, the thermal conductivity layer 120 comprises a variety of adhesives and/or structures. For example, in embodiments that involve a flexible tape type material, the base material of the thermal conductivity layer 120 is a generally flexible material. In some embodiments, the base material includes one or more of plastics, adhesives, glues, epoxies, polymers, thermoplastics, silicone, grease, oil, resin, and the like.

In some embodiments, the thermal conductivity layer 120 is deposited on the first chip 100 by one or more of a dispense or blade process. In a dispense process, for example, a material of the thermal conductivity layer 120 is dissolved in a solvent such as, for example IPA, acetone, NMP, or otherwise melted to obtain a viscosity in the range from about 1,000 cps to about 10,000 cps. The liquid or melted material of the thermal conductivity layer 120 is placed in a container, such as a syringe which is then squeezed out onto the first chip 100 by applying a pushing pressure of about 10 psi to about 500 ps. The material of the thermal conductivity layer 120 is thereafter subjected to a thermal baking process having a the temperature of about 100° C. to about 150° C. to remove residue solvent and solidify the thermal conductivity layer 120 on the first chip 100.

In a blade process, for example, a material of the thermal conductivity layer 120 is dissolved in a solvent such as, for example IPA, acetone, NMP or other suitable solvent that provides good solubility to obtain a viscosity in the range from about 1,000 cps to about 10,000 cps. The liquid or melted material of the thermal conductivity layer 120 is placed in a container that combines with a roller and a solid or flexible metal sheet, for example. Through a rolling process, the roller lays out the melted material of the thermal conductivity layer 120 onto a surface of the first chip 100.

In some embodiments, the thermal conductivity layer 120 comprises a polymer material having a conductive filler material. In some embodiments, the conductive filler material is a material having a relatively high thermal conductivity that is compatible with the polymer. Unlike conventional polymer material, the use of a thermally conductive filler material substantially increases the overall thermal conductivity of the polymer material. In some embodiments, the thermally conductive filler material comprises alumina. Alumina has a thermal conductivity that is approximately 30 W/m-K. In some embodiments, the weight percentage of alumina in the polymer material ranges from about 30% to about 99%. In one or more embodiments, the weight percentage of alumina in the polymer material ranges from about 70% to about 95%. Using alumina as the filler material increases the overall thermal conductivity of the thermal conductivity layer 120 to a value that falls within the range provided above (i.e., 3 W/m-K to 10 W/m-K). This is a substantial improvement over the 0.6 W/m-K to 0.8 W/m-K thermal conductivity associated with many polymers.

In some embodiments, alternate filler materials with high thermal conductivity are used in the polymer material in addition to, or as an alternative of, alumina. For example, in some embodiments, one or more of aluminum nitride having a thermal conductivity of around 180 W/m-K, beryllium oxide having a thermal conductivity of around 260 W/m-K, various metallic solids such as aluminum (Al), copper (Cu), silver (Ag), gold (Au), AlN, Al₂O₃, other suitable metals and/or non-metallic solids such as diamond, silicon, and silicon carbide, solder materials such as tin, lead, copper, antimony, silver, carbon nanotubes, graphite, or the like are used in the polymer as filler material. In some embodiments, a combination of two or more of the above described filler materials are used as the filler material, such as a combination of two or more of alumina, aluminum nitride, beryllium oxide, and carbon nanotubes.

One skilled in the art understands that alternate filler materials having high thermal conductivities that are not specifically listed here may be used in accordance with implementations of the present disclosure. In at least some embodiments, a filler material having a relatively high thermal conductivity that is compatible with the polymer material is used. In some embodiments, the weight percentage of the filler material in the polymer material may range from 30% to 99%, more preferably from 70% to 95%.

In some embodiments, thermal conductivity layer 120 is formed by a molding process before being placed on first chip 100. The molding process, in some embodiments, comprises forming the thermal conductivity layer 120 by supplying a polymer material in a liquid or sheeted form. In various embodiments, to prevent bubbles from forming in a subsequent compression process, the polymer material subjected to a vacuum process in which a vacuum is pumped down to a value of about 0.01 Torr to about 10 Torr. Then in the compression process, the polymer material is subjected to a compression force of about 1 kg/cm² to about 10 kg/cm² for a time of about 1 to about 30 minutes at a temperature from about 50° C. to about 200° C. After the compression process, a post mold cure (PMC) process is applied to fully cure the polymer material. In the PMC, the polymer material is subjected to a hot plate or oven, for example at a temperature of about 100° C. to about 200° C. for a process time of about 0.1 hour to about 20 hours. Once the molding process is completed, the polymer material forms thermal conductivity layer 120 that is thereafter placed on first chip 100.

In some embodiments, after the thermal conductivity layer 120 is placed on the first chip 100, the thermal conductivity layer 120 and the first chip 100 are together subjected to a singulation process. The first chip 100 is affixed to a dicing tape or a die frame (not shown) where the first chip 100 and the thermal conductivity layer 120 are die cut or diced along cutting lines to separate the package of the first chip 100 and the thermal conductivity layer 120 into individual units. Each individual unit has a portion of the thermal conductivity layer 120 attached to first chip 100 a by adhesive layer 110. In various embodiments, the individual units are formed by other methods in addition to or as an alternative of a die cutting process.

FIG. 3 illustrates the thermal conductivity layer 120 being placed on top of first chip 100 a after singulation, in accordance with one or more embodiments.

FIG. 4 illustrates individual units having the first chips 100 a and the thermal conductivity layer 120, wherein the thermal conductivity layer 120 is formed having different shapes first chips 100 a, according to various embodiments.

FIG. 5 is a cross-sectional view of a portion of the semiconductor package 125 having thermal conductivity layers 120 formed on first chips 100 a at a stage of fabrication according to one or more embodiments of the present disclosure. FIG. 5 shows a first substrate 130 a. The semiconductor package includes a first substrate 130 a. In some embodiments, the first substrate 130 a is a wafer carrier. First substrate 130 a has first chips 100 a attached to a surface thereto by a substrate adhesive layer 510. In some embodiments, the substrate adhesive layer 510 comprises a same material as the adhesive layer 110. In other embodiments, the substrate adhesive layer 510 comprises a different material than the adhesive layer 110. Attached to first chips 100 a are thermal conductivity layers 120. First substrate 130 a acts as a temporary support substrate or carrier to facilitate wafer handling, transport, and processing. First substrate 130 a comprises a combination of a silicon substrate, a glass substrate, a polymer substrate, a polymer-based composite substrate, a thick tape, or other suitable material. First substrate 130 a, in some embodiments, is a rigid carrier configured to reduce wafer warping and/or to prevent wafer breakage that often occurs during handling and processing.

In some embodiments, a second chip 100 b is attached to first substrate 130 a. Second chip 100 b comprises any of memory chips, RF (radio frequency) chips, logic chips, or similar chips that are not temperature sensitive or prone to overheating like first chips 100 a.

A molding compound 140 is formed over first substrate 130 a and encapsulates the thermal conductivity layers 120, first chips 100 a, and second chips 100 b. The molding compound 140 is configured to provide package stiffness, a protective or hermetic cover, shielding, and/or provide a heat conductive path to prevent chip overheating. Molding compound 140 comprises any material such as epoxy, epoxy with thermally conductive filler materials, organic cylinders, plastic molding compound, plastic molding compound with fiber, or other suitable material. In some embodiments, molding compound 140 is formed by a spin-on coating process, an injection molding process, and/or the like.

FIG. 6a is a cross-sectional view of the semiconductor package 125, after the molding compound 140 is formed on first substrate 130 a, and the molding compound 140 is planarized, in accordance with one or more embodiments. In some embodiments, the molding compound 140 is planarized by a chemical mechanical polishing (CMP) process, for example. Mechanical grinding processes such as CMP sometimes cause damage to the semiconductor package 125. Accordingly, in some embodiments, a method less likely to cause damage such as, for example, wet chemical etching, dry chemical etching, dry polishing, plasma etching, or other suitable etching processes is used to planarize the molding compound 140.

FIG. 6b is a cross-sectional view of the semiconductor package 125 having the molding compound 140 formed over first substrate 130 a by a sheet lamination process, in accordance with one or more embodiments. Unlike a spin-on coating process, for example, a sheet lamination process makes it possible to eliminate backside grinding because the uniformity and film thickness of the sheets is controllable.

FIG. 7 is a cross-sectional view of the semiconductor package 125 in an inverted position, having been flipped following a planarization process, in accordance with one or more embodiments. The semiconductor package 125 is flipped over so that the molding compound 140 side of the package is bonded to a second substrate 130 b. In some embodiments, second substrate 130 b is a wafer carrier. In some embodiments, the semiconductor package 125 is released from the first substrate 130 a and the chip side of the semiconductor package 125 is bonded to a package substrate 150. In other embodiments, the first substrate 130 a remains attached to the semiconductor package 125 to become the package substrate 150. In some embodiments, package substrate 150 has formed therein any of several additional microelectronic layers such as RDLs (redistribution layers) and microelectronic materials such as conductor materials, semiconductor materials, and dielectric materials. In some embodiments, package substrate 150 also includes active and passive devices (not shown).

FIG. 8 is a cross-sectional view of the semiconductor package 125 having been released from the second substrate 130 b, in accordance with one or more embodiments. The semiconductor package 125 is mounted onto a board 170, such as a printed circuit board (PCB) by electrical connectors 160, such as ball grid array (BGA). In some embodiments, the electrical connectors 160 comprise lead free solder or the like.

FIG. 9 is a cross-sectional view of a portion of a semiconductor package 125 at a stage of fabrication, in accordance with one or more embodiments. Referring back to FIG. 6a , after forming the molding compound 140 over first substrate 130 a, the molding compound 140 is planarized by a chemical mechanical polishing (CMP) process, for example to remove the molding compound 140 to expose the thermal conductivity layer 120, as shown in FIG. 9. In some embodiments, mechanical grinding processes such as CMP often cause damage to the semiconductor package 125. Accordingly, in some embodiments, a method less likely to cause damage such as, for example, wet chemical etching, dry chemical etching, dry polishing, plasma etching, or other suitable etching processes is used to planarize the molding compound 140. By exposing thermal conductivity layers 120, heat generated by the chips is directly and/or efficiently dissipated to the ambient or to a heat sink as heat does not need to go through a molding compound, a barrier to heat dissipation.

FIG. 10 is a cross-sectional view of a portion of the semiconductor package 125 having been released from the first semiconductor 130 a, in accordance with one or more embodiments. The chip side of the semiconductor package 125 is bonded to the package substrate 150. Package substrate 150 has formed therein any of several additional microelectronic layers such as RDLs (redistribution layers) and microelectronic materials such as conductor materials, semiconductor materials, and dielectric materials. Package substrate 150 also includes, in some embodiments, active and passive devices (not shown). A thermal interface material (TIM) 180 is dispensed on top of the thermal conductivity layer 120, molding compound 140 and second chip 100 b. In some embodiments, shown in FIG. 11, the thermal conductivity layer 120 may have a recess within an upper surface facing the TIM 180, as described above in FIG. 4. In some embodiments (not shown), upper surfaces of the thermal conductivity layer may have different shaped recesses and/or a different numbers of recesses over different chips. The different shaped recesses and/or different number of recesses allows for different amounts of heat to be dissipated from the different chips. In some embodiments, TIM 180 comprises a thermally conductive and electrically insulative material, such as an epoxy, like an epoxy mixed with a metal like silver or gold, a “thermal grease,” a “white grease,” other suitable material, or a combination thereof. In some embodiments, a thermal management device 190 such as a heat sink is placed on the TIM 180 to facilitate the dissipation of heat from first chips 100 a and second chip 100 b. In some embodiments, the semiconductor package 125 is mounted onto board 170, such as a printed circuit board (PCB) by electrical connectors 160, such as ball grid array (BGA). In some embodiments, the electrical connectors 160 comprise lead free solder or the like.

FIGS. 12-16 are cross-sectional views of a portion of a semiconductor package at various stages of fabrication according to one or more alternative embodiments of the present disclosure.

FIG. 12 is a cross-sectional view of a portion of the semiconductor package 125 having a thermal conductivity layer 120 formed on a first chip 100 a and a second chip 100 b at a stage of fabrication according to one or more embodiments of the present disclosure. The thermal conductivity layer 120 is not formed on a third chip 100 c. The semiconductor package 125 includes a first substrate 130 a. The first substrate 130 a has the first chip 100 a, the second chip 100 b, and the third chip 100 c attached to a surface thereto by a substrate adhesive layer 510.

The thermal conductivity layer 120 above the first chip 100 a has a first thickness ti, while thermal conductivity layer 120 above the second chip 100 b has a second thickness t₂ that is different than the first thickness t₁. In some embodiments, first thickness ti is greater than second thickness t₂. In some embodiments, top surfaces of the thermal conductivity layer 120 over the first chip 100 a, the thermal conductivity layer 120 over the second chip 100 b, and the third chip 100 c are substantially planar. In other embodiments (not shown), top surfaces of the thermal conductivity layer 120 over the first chip 100 a and the thermal conductivity layer 120 over the second chip 100 b may be higher (i.e., further from the first substrate 130 a) than a top surface of the third chip 100 c. In some embodiments, the adhesive layer 110 contacts the second chip 100 b along an interface that is disposed along a horizontal line that extends through sidewalls of the thermal conductivity layer 120 on the first chip 100 a and sidewalls of the third chip 100 c.

A molding compound 140 is formed over the first substrate 130 a and encapsulates the thermal conductivity layer 120, the first chip 100 a, the second chip 100 b, and the third chip 100 c. FIG. 13 is a cross-sectional view of the semiconductor package 125, after the molding compound 140 is formed on the first substrate 130 a.

FIG. 14 is a cross-sectional view of the semiconductor package 125 in an inverted position, having been flipped, in accordance with one or more embodiments. The semiconductor package 125 is flipped over so that the molding compound 140 side of the package is bonded to a second substrate 130 b. In some embodiments, the second substrate 130 b is a wafer carrier. In some embodiments, the semiconductor package 125 is released from the first substrate 130 a and the chip side of the semiconductor package 125 is bonded to a package substrate 150. In other embodiments, the first substrate 130 a remains attached to the semiconductor package 125 to become the package substrate 150. In some embodiments, package substrate 150 has formed therein any of several additional microelectronic layers such as RDLs (redistribution layers) and microelectronic materials such as conductor materials, semiconductor materials, and dielectric materials.

FIG. 15 is a cross-sectional view of the semiconductor package 125 having been released from the second substrate 130 b, in accordance with one or more embodiments. After release of the semiconductor package 125 from the second substrate 130 b, the molding compound 140 may be planarized.

Planarization of the molding compound 140 removes a part of the molding compound 140, so as to expose top surfaces of the thermal conductivity layer 120 directly over the first chip 100 a and the second chip 100 b, and to further expose a top surface of the third chip 100 c. After the planarization, the thermal conductivity layer 120 directly over the first chip 100 a, the thermal conductivity layer 120 directly over the second chip 100 b, and the third chip 100 c extend to a top surface of the molding compound 140. In some embodiments, a combined height of the first chip 100 a and the thermal conductivity layer 120 above the first chip 100 a is substantially equal to a height of the third chip 100 c. In some embodiments, after planarization is completed, sidewalls of second chip 100 b continuously extend between a bottom of the molding compound 140 and a top of the molding compound 140.

In some embodiments, the molding compound 140 is planarized by a chemical mechanical polishing (CMP) process, for example. In other embodiments, the molding compound 140 is planarized by wet chemical etching, dry chemical etching, dry polishing, plasma etching, or other suitable etching processes. In some embodiments, the planarization process used to planarize the molding compound 140 may also remove parts of the thermal conductivity layer 120 directly over the first chip 100 a and the second chip 100 b, so that the thermal conductivity layer 120 directly over the first chip 100 a, the thermal conductivity layer 120 directly over the second chip 100 b, and the third chip 100 c extend to a top surface of the molding compound 140.

FIG. 16 is a cross-sectional view of the semiconductor package 125 having been mounted onto a board 170, such as a printed circuit board (PCB) by electrical connectors 160, such as ball grid array (BGA). In some embodiments, the electrical connectors 160 comprise lead free solder or the like. The chip side of the semiconductor package 125 is bonded to the package substrate 150. A thermal interface material (TIM) 180 is formed to be in physical contact with top surfaces of the thermal conductivity layer 120 directly over the first chip 100 a, the thermal conductivity layer 120 directly over the second chip 100 b, the molding compound 140, and the third chip 100 c. In some embodiments, a thermal management device 190 such as a heat sink is placed on the TIM 180 to facilitate the dissipation of heat from the first chip 100 a, the second chip 100 b, and the third chip 100 c.

In one or more embodiments, the thermal conductivity layer in a semiconductor package provides a high degree of heat dissipation by providing a thermal path through which thermal energy, or heat that is generated by a chip to be dissipated to the ambient or environment.

In one or more embodiments, use of the thermal conductivity layer allows heat generated by temperature sensitive chips to be effectively and/or efficiently dissipated to the ambient or to a thermal management device to prevent overheating of the chip.

In one or more embodiments, the thermal conductivity layer can function as a mechanical support during molding to minimize molding compound shrinkage and/or warpage.

One aspect of this description relates to a method of forming a semiconductor package includes forming a thermal conductivity layer and attaching the thermal conductivity layer to a chip, the chip having a first surface and a second surface, the thermal conductivity layer being attached to the first surface of the chip, wherein the thermal conductivity layer is configured to provide a path through which heat generated from the chip is dissipated. The method also includes attaching a substrate to the second surface of the chip. The method further includes forming a molding compound above the substrate to encapsulate the chip and the thermal conductivity layer.

Another aspect of this description relates to a semiconductor package that includes a chip attached to a first substrate. The semiconductor package also includes a thermal conductivity layer attached to the chip, wherein the thermal conductivity layer provides a path through which heat generated from the chip is dissipated. The semiconductor package further includes a molding compound formed above the first substrate, the molding compound encapsulating the chip and the thermal conductivity layer.

In the preceding detailed description, specific exemplary embodiments have been described. It will, however, be apparent to a person of ordinary skill in the art that various modifications, structures, processes, and changes may be made thereto without departing from the broader spirit and scope of the present disclosure. The specification and drawings are, accordingly, to be regarded as illustrative and not restrictive. It is understood that embodiments of the present disclosure are capable of using various other combinations and environments and are capable of changes or modifications within the scope of the claims and their range of equivalents. 

What is claimed is:
 1. A method of forming a semiconductor package, comprising: attaching a first thermal conductivity layer to an upper surface of a first chip; attaching a second thermal conductivity layer to an upper surface of a second chip; attaching a first support substrate to lower surfaces of the first chip and the second chip; forming a molding compound over the first support substrate and laterally surrounding the first chip and the second chip; and replacing the first support substrate with a package substrate after forming the molding compound over the first support substrate.
 2. The method of claim 1, further comprising: removing a part of the molding compound to expose upper surfaces of the first thermal conductivity layer and the second thermal conductivity layer; and forming a thermal interface material to directly contact the upper surfaces of the first thermal conductivity layer and the second thermal conductivity layer.
 3. The method of claim 2, further comprising: attaching the first support substrate to a lower surface of a third chip, wherein the third chip has a third height that is greater than a first height of the first chip and a second height of the second chip; and forming the molding compound over the third chip.
 4. The method of claim 3, wherein the first height is less than the second height; and wherein the third height is substantially equal to a first sum of the first height and a first thickness of the first thermal conductivity layer and to a second sum of the second height and a second thickness of the second thermal conductivity layer.
 5. The method of claim 3, further comprising: removing the part of the molding compound to expose an upper surface of the third chip; and forming the thermal interface material to directly contact the upper surface of the third chip.
 6. The method of claim 1, further comprising: attaching a second support substrate to the molding compound, the molding compound separating the second support substrate from upper surfaces of the first thermal conductivity layer and the second thermal conductivity layer; and replacing the first support substrate with the package substrate, the molding compound between the package substrate and the second support substrate.
 7. The method of claim 6, further comprising: removing the second support substrate and a part of the molding compound after replacing the first support substrate with the package substrate.
 8. The method of claim 1, further comprising: forming the first thermal conductivity layer on the first chip; and dicing the first chip, after forming the first thermal conductivity layer onto the first chip, to define a plurality of chips comprising the first chip.
 9. The method of claim 1, wherein the first thermal conductivity layer has a thickness that varies between outermost sidewalls of the first thermal conductivity layer.
 10. A method of forming a semiconductor package, comprising: attaching a first thermal conductivity layer to an upper surface of a first chip, wherein the first thermal conductivity layer and the first chip collectively have a first height; attaching a second thermal conductivity layer to an upper surface of a second chip, wherein the second thermal conductivity layer and the second chip collectively have a second height that is substantially equal to the first height; attaching a first support substrate to lower surfaces of the first chip and the second chip; forming a molding compound over the first support substrate and around the first chip and the second chip; attaching the molding compound to a second support substrate; and replacing the first support substrate with a package substrate.
 11. The method of claim 10, wherein the first thermal conductivity layer comprises carbon nanotubes or carbon fibers.
 12. The method of claim 10, wherein the first thermal conductivity layer comprises a carbon related material.
 13. The method of claim 10, wherein the first thermal conductivity layer has a greater thickness along outermost sidewalls of the first thermal conductivity layer than at a center of the first thermal conductivity layer.
 14. A method of forming a semiconductor package, comprising: attaching a first thermal conductivity layer to a first chip; attaching a second thermal conductivity layer to a second chip; attaching the first chip and the second chip to a substrate; and forming a molding compound around the first chip and the second chip.
 15. The method of claim 14, wherein the first thermal conductivity layer comprises a polymer material having a conductive filler material.
 16. The method of claim 15, wherein a weight percentage of the conductive filler material is in a range of between 70% to 95%.
 17. The method of claim 15, further comprising: attaching the molding compound to a support substrate; and replacing the substrate with a package substrate, the molding compound between the package substrate and the support substrate.
 18. The method of claim 15, further comprising: attaching the substrate to a conductive bump, wherein the molding compound covers upper surfaces of the first thermal conductivity layer and the second thermal conductivity layer when attaching the substrate to the conductive bump.
 19. The method of claim 15, further comprising: attaching a third chip to the substrate, the third chip having a third height that is greater than a first height of the first chip and a second height of the second chip, wherein the first height is greater than the second height; and wherein the third height is substantially equal to a first sum of the first height and a first thickness of the first thermal conductivity layer and to a second sum of the second height and a second thickness of the second thermal conductivity layer.
 20. The method of claim 15, further comprising: attaching a third chip to the substrate, the third chip having a height that is substantially equal to a distance between a bottom of the first chip and a top of the first thermal conductivity layer; forming the molding compound over the third chip; and removing a part of the molding compound to expose upper surfaces of the first thermal conductivity layer, the second thermal conductivity layer, and the third chip. 